"B.B." u wrote in message
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A piston less than 1/4" across has an area of 1/2 a square inch, so
20psi oil pressure gets you ten pounds of force,

No, that would be 5/100 sq" (.049) for a 1/4" dia. piston (extend, only.
The rod would reduce the retract area and force.)

So, for a 1/4" piston, you get just under ONE pound for 20psi.

LLoyd